Well. To be fair. We don't know everything about reality, so aren't in a position to state definitively even what it is - happy for you to correct me. Do you know what reality is? What is it for? If it's for nothing and random, do we know that? if it's for something and not random, do we know that? Is there just one reality or more than one? Will we ever know? Is it ever knowable.
This sounds like a 'God of the gaps' argument.
Regarding aliens, it seems a strange position to think they don't or can't exist in the reality that we think we belong to. Our Earth is 4 billion years old and in that time it's evolved a middling, backward race that has lurched from the surface into (very) local solar system travel. Planets that formed earlier by a magnitude of millions or billions of years are likely to be ahead of us. To think that aliens don't and can't exist ironically goes back to religion itself - the idea that the Earth was 'special' and the 'centre of the Universe' - people like Galileo Galilei showed us that the Earth wasn't the centre of the universe and actually orbited around the sun. Since then we've found that our galaxy isn't even special and that our Solar System orbits around it. Our galaxy itself orbits around the local group, which in turn orbits around the virgo supercluster (Loosely, to be fair).
I do not recall anyone in this thread stating that aliens do not exist. The problem is supposing that any aliens would be close enough to Earth to travel here in any kind of reasonable time frame.
We do not understand all the barriers for life to start, evolve, and avoid being snuffed out before being technologically advanced enough to attempt any form of spaceflight, let alone travel between distant stars.* We have observed no good evidence for aliens, anywhere, at any distance from Earth.
https://en.wikipedia.org/wiki/Great_FilterThere are fundamental barriers to space travel between the stars. It would take extraordinary effort (and a very long time) to travel to even the nearest star. Any alien race would need to be very motivated and think very far ahead to consider such a journey - and this is just to the closest star, which is highly unlikely to be interesting.
We have been sending out radio signals for a little over 100 years. Those signals have reached less than 100 star systems. That's extremely small pool of planets which might be inhabited by intelligent space-faring aliens who might wish to visit Earth. And then, there is all the tine it would take for then to reach here here. Even if they set off after detecting our earliest signals (which were weak and easily missed or lost in background noise at those distances), and possessed some really advanced propulsion systems which gets them to a significant proportion of the speed of light, you are surely only talking about the nearest few stars from where they could have conceivably set off. The pool has now shrunk to just a few stars at best, and we have yet to detect evidence of alien life, let alone advanced technology, in the whole of the observable universe.
* The chances of highly technologically advanced life existing within our local group would seem remote in the extreme.
It seems difficult to imagine that they can get to Earth at all, given the distances, but even our race have thought of ways to breach the interstellar vastness - Colony Ships, Warping of space/time, Hypersleep and the like. But that's assuming that our imagining of what reality is, is correct. If other dimensions exist (Via something like branes) then perhaps travel could be based on moving between the edges rather than having to physically move through space.
They would need to breach some fundamental physics for this highly speculative 'means of travel'. And once they have cracked that nugget, they would need to repeatedly fuck up the parking job and crash at the end of the journey.
Colony ships are just about conceivable, I guess. It would require a truly massive project and surely would be a desperate act. But why would they travel to Earth? Why would they suppose
that's the place we should go? Because, surely, they would need to have set off long before there was any evidence of intelligent life on Earth which is detectable from a distant star.
'Hypersleep', same basic problems.
As for 'higher dimensional aliens' - even if higher dimensions exist in reality (instead of purely within mathematical models), the maths makes for a universe which cannot exist in a useful fashion. So, you can use maths to model higher dimensions, but the same mathematical modelling leads to problems with gravity and other forces.
<![CDATA[<a href="https://www.youtube.com/v/y2i3kZVcG5s" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">https://www.youtube.com/v/y2i3kZVcG5s</a>]]>Who knows? It's a possible and I don't know enough about our reality to prove or disprove anything - especially using something as absurd as 'common sense' (See Ester McVeigh). So my mind becomes open. If aliens aren't walking among us then I will be unsurprised. If aliens are walking among us then I'll be a bit surprised, but not massively. If reality turns out to be exactly what we think it is, I'll be unsurprised. If reality turns out to be something entirely different than what we think then I'll be surprised, but not massively.
'Walking amongst us' seems an absurd proposition.* On the one hand, aliens regularly fuck up their parking jobs when reaching earth, and their space ships are detectable; and on the other, they have the ability to disguise their appearance to the point where they can walk amongst us undetected (and avoid all accidents). The whole idea is plucked out of thin air, and based upon pictures and videos which are not immediately explainable to all people (or are outright hoaxes).
* Yes, I realise you might not have meant that literally, but still, you wrote it, so I addressed it.
We haven't got all the answers and the more answers we get, the more questions remain. Humanity has been at this science lark seriously for maybe 1,000 years - modern science for a few hundred years. It's reasonable to assume that if a civillisation has existed for millions or billions of years then (to quote Arthur C. Clarke's three laws) :-
1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
3. Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clark was a good fellow, an undersea explorer, and TV host. He studied mathematics and physics at university. But his was not a practicing scientist (some electrical engineering from WWII). He primarily worked as a science fiction writer. Perhaps his comments on the matters of science and scientists should be considered within those contexts.
The problems to be overcome by alien race in science are basic and fundamental. They would first need to be aware of us. They would need to have discovered something completely at odds with all known science, and then to have exploited it to travel huge distances. And, then would need to be local - real local (cosmologically speaking) - the nearest few stars. So, all that. Or, it is a mixture of technical glitches, optical artifacts, weather phenomenon; and hoaxes. All of which are generally understood.
"We haven't got all the answers and the more answers we get, the more questions remain." This takes me back to my opening remarks - it 'God of the gaps' stuff. I'd love to be proven wrong. But their is just no good evidence for aliens visiting Earth, interdimensional travel, etc. On the contrary, all the available evidence is against these things.
